LIGHT signaling through LTβR and HVEM in keratinocytes promotes psoriasis and atopic dermatitis-like skin inflammation

Psoriasis (PS) and atopic dermatitis (AD) are common skin inflammatory diseases characterized by hyper-responsive keratinocytes. Although, some cytokines have been suggested to be specific for each disease, other cytokines might be central to both diseases. Here, we show that Tumor necrosis factor superfamily member 14 (TNFSF14), known as LIGHT, is required for experimental PS, similar to its requirement in experimental AD. Mice devoid of LIGHT, or deletion of either of its receptors, lymphotoxin β receptor (LTβR) and herpesvirus entry mediator (HVEM), in keratinocytes, were protected from developing imiquimod-induced psoriatic features, including epidermal thickening and hyperplasia, and expression of PS-related genes. Correspondingly, in single cell RNA-seq analysis of PS patient biopsies, LTβR transcripts were found strongly expressed with HVEM in keratinocytes, and LIGHT was upregulated in T cells. Similar transcript expression profiles were also seen in AD biopsies, and LTβR deletion in keratinocytes also protected mice from allergen-induced AD features. Moreover, in vitro, LIGHT upregulated a broad spectrum of genes in human keratinocytes that are clinical features of both PS and AD skin lesions. Our data suggest that agents blocking LIGHT activity might be useful for therapeutic intervention in PS as well as in AD.

OX40 in the Pathogenesis of Atopic Dermatitis-A New Therapeutic Target

Atopic dermatitis (AD) is a chronic, heterogeneous, inflammatory disease characterized by skin lesions, pruritus, and pain. Patients with moderate-to-severe AD experience chronic symptoms, intensified by unpredictable flares, and often have comorbidities and secondary complications, which can result in significant clinical burden that impacts the patient's overall quality of life. The complex interplay of immune dysregulation and skin barrier disruption drives AD pathogenesis, of which T-cell-dependent inflammation plays a critical role in patients with AD. Despite new targeted therapies, many patients with moderate-to-severe AD fail to achieve or sustain their individual treatment goals and/or may not be suitable for or tolerate these therapies. There remains a need for a novel, efficacious, well-tolerated therapeutic option that can deliver durable benefits across a heterogeneous AD patient population. Expression of OX40 [tumor necrosis factor receptor superfamily, member 4 (TNFRSF4)], a prominent T-cell co-stimulatory molecule, and its ligand [OX40L; tumor necrosis factor superfamily, member 4 (TNFSF4)] is increased in AD. As the OX40 pathway is critical for expansion, differentiation, and survival of effector and memory T cells, its targeting might be a promising therapeutic approach to provide sustained inhibition of pathogenic T cells and associated inflammation and broad disease control. Antibodies against OX40 [rocatinlimab (AMG 451/KHK4083) and telazorlimab (GBR 830)] or OX40L [amlitelimab (KY1005)] have shown promising results in early-phase clinical studies of moderate-to-severe AD, highlighting the importance of OX40 signaling as a new therapeutic target in AD.

Late-rising CD4 T cells resolve mouse cytomegalovirus persistent replication in the salivary gland

Conventional antiviral memory CD4 T cells typically arise during the first two weeks of acute infection. Unlike most viruses, cytomegalovirus (CMV) exhibits an extended persistent replication phase followed by lifelong latency accompanied with some gene expression. We show that during mouse CMV (MCMV) infection, CD4 T cells recognizing an epitope derived from the viral M09 protein only develop after conventional memory T cells have already peaked and contracted. Ablating these CD4 T cells by mutating the M09 genomic epitope in the MCMV Smith strain, or inducing them by introducing the epitope into the K181 strain, resulted in delayed or enhanced control of viral persistence, respectively. These cells were shown to be unique compared to their conventional memory counterparts; producing higher IFNγ and IL-2 and lower IL-10 levels. RNAseq analyses revealed them to express distinct subsets of effector genes as compared to classical CD4 T cells. Additionally, when M09 cells were induced by epitope vaccination they significantly enhanced protection when compared to conventional CD4 T cells alone. These data show that late-rising CD4 T cells are a unique memory subset with excellent protective capacities that display a development program strongly differing from the majority of memory T cells.

TNF-like weak inducer of apoptosis inhibition is comparable to IL-13 blockade in ameliorating atopic dermatitis inflammation

BACKGROUND

Targeting IL-13 is highly efficacious in patients with Th2-biased atopic dermatitis (AD), but inhibition of other inflammatory molecules might also limit disease. We investigated the importance of the TNF family cytokine TNF-like weak inducer of apoptosis (TWEAK; TNFSF12) to keratinocyte dysregulation and the pathogenesis of AD in mice and also tested if blocking TWEAK has a similar therapeutic effect as targeting IL-13.

METHODS

Conditional knockout mice lacking Fn14 (TNFRSF12A), the receptor for TWEAK, only in keratinocytes, were repetitively sensitized with house dust mite allergen and analyzed for AD-like skin inflammation. To determine the translational potential, wild-type mice with AD were therapeutically treated with anti-TWEAK and/or anti-IL-13 antibodies, and skin inflammation was assessed.

RESULTS

Mice deficient in Fn14 in keratinocytes were resistant to developing maximal clinical features of AD, exhibiting reduced epidermal hyperplasia and dermal thickening, less skin infiltration of immune cells, and downregulated inflammatory gene expression. Moreover, therapeutic neutralization of TWEAK in wild-type mice with AD reduced all of the pathological features to a comparable extent as blocking IL-13.

CONCLUSIONS

The activity of TWEAK in keratinocytes contributes to AD development, and neutralizing TWEAK represents a future potential therapeutic option in human AD similar to targeting IL-13.

Agonism of 4-1BB for immune therapy: a perspective on possibilities and complications

Costimulatory receptors on immune cells represent attractive targets for immunotherapy given that these molecules can increase the frequency of individual protective immune cell populations and their longevity, as well as enhance various effector functions. 4-1BB, a member of the TNF receptor superfamily, also known as CD137 and TNFRSF9, is one such molecule that is inducible on several cell types, including T cells and NK cells. Preclinical studies in animal models have validated the notion that stimulating 4-1BB with agonist reagents or its natural ligand could be useful to augment conventional T cell and NK cell immunity to protect against tumor growth and against viral infection. Additionally, stimulating 4-1BB can enhance regulatory T cell function and might be useful in the right context for suppressing autoimmunity. Two human agonist antibodies to 4-1BB have been produced and tested in clinical trials for cancer, with variable results, leading to the production of a wealth of second-generation antibody constructs, including bi- and multi-specifics, with the hope of optimizing activity and selectivity. Here, we review the progress to date in agonism of 4-1BB, discuss the complications in targeting the immune system appropriately to elicit the desired activity, together with challenges in engineering agonists, and highlight the untapped potential of manipulating this molecule in infectious disease and autoimmunity.

Anti-CD3 inhibits circulatory and tissue-resident memory CD4 T cells that drive asthma exacerbations in mice

BACKGROUND

Exacerbations of asthma are thought to be strongly dependent on reactivation of allergen-induced lung tissue-resident and circulatory memory CD4 T cells. Strategies that broadly inhibit multiple T cell populations might then be useful to limit asthma. Accordingly, we tested whether targeting CD3 during exposure to inhaled allergen could prevent the accumulation of lung-localized effector memory CD4 T cells and block exacerbations of asthmatic inflammation.

METHODS

House dust mite-sensitized and repetitively challenged BL/6 mice were transiently treated therapeutically with F(ab')2 anti-CD3ε and memory T cell responses and lung inflammation were assessed. PBMCs from HDM-allergic donors were examined for the effect of anti-CD3 on expansion of allergen-reactive T cells.

RESULTS

Allergen-sensitized mice undergoing exacerbations of asthma were protected from lung inflammation by transient therapeutic treatment with F(ab')2 anti-CD3. Regardless of whether sensitized mice underwent a secondary or tertiary recall response to inhaled allergen, anti-CD3 inhibited all phenotypes of effector memory CD4 T cells in the lung tissue and lung vasculature by 80%-90%, including those derived from tissue-resident and circulatory memory T cells. This did not depend on Treg cells suggesting it was primarily a blocking effect on memory T cell signaling. Correspondingly, anti-CD3 also strongly inhibited proliferation of human allergen-reactive memory CD4 T cells from allergic individuals. In contrast, the number of surviving tissue-resident memory CD4 T cells that were maintained in the lungs at later times was not robustly reduced by anti-CD3.

CONCLUSION

Anti-CD3 F(ab')2 administration at the time of allergen exposure represents a viable strategy for limiting the immediate activity of allergen-responding memory T cells and asthma exacerbations.

Lymphotoxin beta receptor signaling directly controls airway smooth muscle deregulation and asthmatic lung dysfunction

BACKGROUND

Dysregulation of airway smooth muscle cells (ASM) is central to the severity of asthma. Which molecules dominantly control ASM in asthma is unclear. High levels of the cytokine LIGHT (aka TNFSF14) have been linked to asthma severity and lower baseline predicted FEV1 percentage, implying that signals through its receptors might directly control ASM dysfunction.

OBJECTIVE

Our study sought to determine whether signaling via lymphotoxin beta receptor (LTβR) or herpesvirus entry mediator from LIGHT dominantly drives ASM hyperreactivity induced by allergen.

METHODS

Conditional knockout mice deficient for LTβR or herpesvirus entry mediator in smooth muscle cells were used to determine their role in ASM deregulation and airway hyperresponsiveness (AHR) in vivo. Human ASM were used to study signals induced by LTβR.

RESULTS

LTβR was strongly expressed in ASM from normal and asthmatic subjects compared to several other receptors implicated in smooth muscle deregulation. Correspondingly, conditional deletion of LTβR only in smooth muscle cells in smMHCCreLTβRfl/fl mice minimized changes in their numbers and mass as well as AHR induced by house dust mite allergen in a model of severe asthma. Intratracheal LIGHT administration independently induced ASM hypertrophy and AHR in vivo dependent on direct LTβR signals to ASM. LIGHT promoted contractility, hypertrophy, and hyperplasia of human ASM in vitro. Distinguishing LTβR from the receptors for IL-13, TNF, and IL-17, which have also been implicated in smooth muscle dysregulation, LIGHT promoted NF-κB-inducing kinase-dependent noncanonical nuclear factor kappa-light-chain enhancer of activated B cells in ASM in vitro, leading to sustained accumulation of F-actin, phosphorylation of myosin light chain kinase, and contractile activity.

CONCLUSIONS

LTβR signals directly and dominantly drive airway smooth muscle hyperresponsiveness relevant for pathogenesis of airway remodeling in severe asthma.

Experimental Melanoma Immunotherapy Model Using Tumor Vaccination with a Hematopoietic Cytokine

Fms-like tyrosine kinase 3 ligand (Flt3L) is a hematopoietic cytokine that promotes the survival and differentiation of dendritic cells (DCs). It has been used in tumor vaccines to activate innate immunity and enhance antitumor responses. This protocol demonstrates a therapeutic model using cell-based tumor vaccine consisting of Flt3L-expressing B16-F10 melanoma cells along with phenotypic and functional analysis of immune cells in the tumor microenvironment (TME). Procedures for cultured tumor cell preparation, tumor implantation, cell irradiation, tumor size measurement, intratumoral immune cell isolation, and flow cytometry analysis are described. The overall goal of this protocol is to provide a preclinical solid tumor immunotherapy model, and a research platform to study the relationship between tumor cells and infiltrating immune cells. The immunotherapy protocol described here can be combined with other therapeutic modalities, such as immune checkpoint blockade (anti-CTLA-4, anti-PD-1, anti-PD-L1 antibodies) or chemotherapy in order to improve the cancer therapeutic effect of melanoma.

A Deficiency in the Cytokine TNFSF14/LIGHT Limits Inflammation and Remodeling in Murine Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is a chronic type 2 allergic disease, with esophageal tissue remodeling as the mechanism behind clinical dysphagia and strictures. IL-13 is thought to be a central driver of disease, but other inflammatory factors, such as IFNs and TNF superfamily members, have been hypothesized to play a role in disease pathogenesis. We recently found that the cytokine TNFSF14/LIGHT is upregulated in the esophagus of patients with EoE and that LIGHT promotes inflammatory activity in esophageal fibroblasts. However, the global effects of LIGHT on EoE pathogenesis in vivo remain unknown. We investigated the impact of a LIGHT deficiency in a murine model of EoE driven by house dust mite allergen. Chronic intranasal challenge with house dust mite promoted esophageal eosinophilia and increased CD4+ T cell numbers and IL-13 and CCL11 production in wild-type mice. Esophageal remodeling was reflected by submucosal collagen accumulation, increased muscle density, and greater numbers of fibroblasts. LIGHT-/- mice displayed normal esophageal eosinophilia, but exhibited reduced frequencies of CD4 T cells, IL-13 expression, submucosal collagen, and muscle density and a decrease in esophageal accumulation of fibroblasts. In vitro, LIGHT increased division of human esophageal fibroblasts and selectively enhanced IL-13-mediated expression of a subset of inflammatory and fibrotic genes. These results show that LIGHT contributes to various features of murine EoE, impacting the accumulation of CD4 T cells, IL-13 production, fibroblast proliferation, and esophagus remodeling. These findings suggest that LIGHT may be, to our knowledge, a novel therapeutic target for the treatment of EoE.

Incisional hernia following colorectal cancer surgery according to suture technique: Hughes Abdominal Repair Randomized Trial (HART)

BACKGROUND

Incisional hernias cause morbidity and may require further surgery. HART (Hughes Abdominal Repair Trial) assessed the effect of an alternative suture method on the incidence of incisional hernia following colorectal cancer surgery.

METHODS

A pragmatic multicentre single-blind RCT allocated patients undergoing midline incision for colorectal cancer to either Hughes closure (double far-near-near-far sutures of 1 nylon suture at 2-cm intervals along the fascia combined with conventional mass closure) or the surgeon's standard closure. The primary outcome was the incidence of incisional hernia at 1 year assessed by clinical examination. An intention-to-treat analysis was performed.

RESULTS

Between August 2014 and February 2018, 802 patients were randomized to either Hughes closure (401) or the standard mass closure group (401). At 1 year after surgery, 672 patients (83.7 per cent) were included in the primary outcome analysis; 50 of 339 patients (14.8 per cent) in the Hughes group and 57 of 333 (17.1 per cent) in the standard closure group had incisional hernia (OR 0.84, 95 per cent c.i. 0.55 to 1.27; P = 0.402). At 2 years, 78 patients (28.7 per cent) in the Hughes repair group and 84 (31.8 per cent) in the standard closure group had incisional hernia (OR 0.86, 0.59 to 1.25; P = 0.429). Adverse events were similar in the two groups, apart from the rate of surgical-site infection, which was higher in the Hughes group (13.2 versus 7.7 per cent; OR 1.82, 1.14 to 2.91; P = 0.011).

CONCLUSION

The incidence of incisional hernia after colorectal cancer surgery is high. There was no statistical difference in incidence between Hughes closure and mass closure at 1 or 2 years.

REGISTRATION NUMBER

ISRCTN25616490 (http://www.controlled-trials.com).

Contribution of circulatory cells to asthma exacerbations and lung tissue-resident CD4 T cell memory

Tissue-resident memory CD4 T cells (Trm) are thought to be a major contributor to asthma relapse, but the role of circulatory T cells in asthma exacerbations or to maintaining the population of lung Trm cells is not fully understood. Here, we used a house dust mite allergen-based murine model of asthma relapse, and monitored the development of lung effector/Trm phenotype CD44hiCD62LloCD69+ CD4 T cells. To determine the contribution of circulatory cells, mice were treated with FTY720, to block lymphocyte egress from lymph nodes. Inhibiting the primary migration of circulatory cells to the lungs mitigated the accumulation and expansion of allergen-driven Trm phenotype cells, but subsequent allergen challenges still resulted in strong lung inflammation and Trm cell accumulation. This was blocked if FTY720 was also given at the time of allergen re-exposure, showing that new circulatory cells contributed to this lung memory/effector T cell pool at times well after the initial sensitization. However, once lung-localized Trm cells developed at high frequency, circulatory cells were not required to maintain this population following allergen re-encounter, even though circulatory cells still were major contributors to the overall asthmatic lung inflammatory response. Our results suggest that strategies that target the response of circulatory memory T cells and Trm cells together might be required to strongly inhibit T cell reactivity to airborne allergens and to limit exacerbations of asthma and their reoccurrence, but the contribution of circulatory T cells might vary in long-term asthmatics possessing a large stable Trm cell population in the lungs.

Realigning the LIGHT signaling network to control dysregulated inflammation

Advances in understanding the physiologic functions of the tumor necrosis factor superfamily (TNFSF) of ligands, receptors, and signaling networks are providing deeper insight into pathogenesis of infectious and autoimmune diseases and cancer. LIGHT (TNFSF14) has emerged as an important modulator of critical innate and adaptive immune responses. LIGHT and its signaling receptors, herpesvirus entry mediator (TNFRSF14), and lymphotoxin β receptor, form an immune regulatory network with two co-receptors of herpesvirus entry mediator, checkpoint inhibitor B and T lymphocyte attenuator, and CD160. Deciphering the fundamental features of this network reveals new understanding to guide therapeutic development. Accumulating evidence from infectious diseases points to the dysregulation of the LIGHT network as a disease-driving mechanism in autoimmune and inflammatory reactions in barrier organs, including coronavirus disease 2019 pneumonia and inflammatory bowel diseases. Recent clinical results warrant further investigation of the LIGHT regulatory network and application of target-modifying therapeutics for disease intervention.

Blocking the Migration of Circulatory T cells Mitigates the Accumulation of Allergen-induced Tissue-Resident Memory T cells

Targeting lymphocyte egress from lymph nodes with S1PR agonists has been approved for multiple sclerosis and colitis, but their potential in asthma is unclear. Tissue-resident memory CD4 T cells (Trm) are thought to be a major contributor to asthma relapse but the role of circulatory T cells is not fully understood. We used a murine model of house dust mite allergen-driven asthma exacerbation and transient i.v. injection of antibody and the Trm markers CD44hi CD62Llo and CD69+ to distinguish lung-localized CD4 T cells from circulatory T cells. Trm were retained in lungs after the initial allergen encounter and expanded upon repeated allergen exposures. To determine the role of circulatory T cells, mice were given FTY720, a S1PR agonist. Blocking the primary migration of circulatory T cells alleviated the formation and accumulation of lung Trm. Even so, subsequent allergen challenges still resulted in strong Trm accumulation. This was blocked if FTY720 was also given during allergen re-exposure showing that new allergen-driven circulatory T cells formed this lung Trm pool at times well after the initial sensitization. In contrast, once lung Trm cells developed at high frequency, they no longer relied on circulatory T cells with their expansion and further survival of the Trm pool being unaffected by FTY720. Overall, this suggests that targeting circulatory T cells during allergen insults might be employed to inhibit the accumulation of lung Trm in individuals with recent-onset asthma and may promote long-lasting airway tolerance. However, in individuals that have had asthma for some time and developed a stable population of lung Trm, targeting circulatory T cells may be ineffective in reducing the pathogenic T cell pool that maintains disease

“Therapeutic targeting of tumor necrosis factor like weak inducer of apoptosis (TWEAK) in psoriasis”

Excessive activity of TNF and IL-17 in keratinocytes can drive psoriatic skin inflammation and their targeting is highly advantageous in psoriasis patients, but whether these cytokines act with other inflammatory molecules is unknown. Previously, we demonstrated with knockout mice that the TNF-related cytokine TWEAK (TNFSF12) was a major driver of skin inflammation in the imiquimod model of psoriasis. Here, we found that mice carrying a deletion of TWEAK’s receptor, Fn14 (TNFRSF12A), specifically in keratinocytes, exhibited reduced psoriasis features, including less epidermal hyperplasia and poor expression of genes associated with human psoriasis. Further, RNA-seq analysis in human keratinocytes demonstrated that TWEAK strongly synergizes with either TNF or IL-17A in upregulating the transcripts for psoriasis-associated chemokines and cytokines, implying that TWEAK co-operates with TNF and IL-17 to enhance feedback inflammatory activity. Correspondingly, administration of anti-TWEAK antibody demonstrated therapeutic efficacy in the psoriasis mouse model and was equally as effective as antibodies to IL-17A or TNF in reducing clinical and immunological features of psoriasis-like skin inflammation, while co-neutralization of TWEAK with either cytokine had no additional therapeutic effect, reinforcing the conclusion that all three cytokines act together. We conclude that TWEAK blockade could be another potential therapeutic avenue in patients with psoriasis that might be equally as useful as blocking TNF and IL-17. Future studies targeting TWEAK in clinical trials for psoriasis may then be warranted.

Supported by NIH grant AR072640

LIGHT controls distinct homeostatic and inflammatory gene expression profiles in esophageal fibroblasts via differential HVEM and LTβR-mediated mechanisms

Fibroblasts mediate tissue remodeling in eosinophilic esophagitis (EoE), a chronic allergen-driven inflammatory pathology. Diverse fibroblast subtypes with homeostasis-regulating or inflammatory profiles have been recognized in various tissues, but which mediators induce these alternate differentiation states remain largely unknown. We recently identified that TNFSF14/LIGHT promotes an inflammatory esophageal fibroblast in vitro. Herein we used esophageal biopsies and primary fibroblasts to investigate the role of the LIGHT receptors, herpes virus entry mediator (HVEM) and lymphotoxin-beta receptor (LTβR), and their downstream activated pathways, in EoE. In addition to promoting inflammatory gene expression, LIGHT down-regulated homeostatic factors including WNTs, BMPs and type 3 semaphorins. In vivo, WNT2B⁺ fibroblasts were decreased while ICAM-1⁺ and IL-34⁺ fibroblasts were expanded in EoE, suggesting that a LIGHT-driven gene signature was imprinted in EoE versus normal esophageal fibroblasts. HVEM and LTβR overexpression and deficiency experiments demonstrated that HVEM regulates a limited subset of LIGHT targets, whereas LTβR controls all transcriptional effects. Pharmacologic blockade of the non-canonical NIK/p100/p52-mediated NF-κB pathway potently silenced LIGHT's transcriptional effects, with a lesser role found for p65 canonical NF-κB. Collectively, our results show that LIGHT promotes differentiation of esophageal fibroblasts toward an inflammatory phenotype and represses homeostatic gene expression via a LTβR-NIK-p52 NF-κB dominant pathway.

Optimising CT-chest protocols and the added value of venous-phase contrast timing; Observational case-control

INTRODUCTION

To optimize CT chest protocol by comparing venous contrast timing with arterial timing for contrast opacification in vessels, qualitative image quality and radiologists' satisfaction and diagnostic confidence in assessing for potential nodal, pleural and pulmonary disease in general oncology outpatients.

METHOD

Matched case-control study performed following CT protocol update. 92 patients with a range of primary malignancies with 2 CT chests in a 2-year period, one with an arterial phase protocol and the second in the 60 second venous phase, were included. Contrast attenuation in aorta, pulmonary artery and liver were measured. Subjective measurements assessed perivenous artefact, confidence in nodal pleural and pulmonary assessment and presence of pulmonary emboli. Statistical analysis was performed using paired and unpaired t-tests.

RESULTS

Venous-phase CT demonstrated more consistent enhancement of the vessels, with higher attenuation of the nodes, pulmonary and pleural lesions. There was a significant reduction in perivenous beam hardening artefact on venous-phase CT (P < 0.001). Diagnostic confidence was significantly higher for nodal assessment and pleural abnormality visibility (P < 0.001) and pleural assessment (P < 0.05). There was no significant difference in pulmonary mass visibility. There was adequate enhancement to diagnose significant pulmonary emboli (PE) with 4 incidental PEs detected on the venous phase, extending to segmental vessels.

CONCLUSION

Venous-phase CT chest performs better than arterial-phase on all fronts, without compromising assessment of incidental pulmonary emboli. When intravenous contrast is indicated in a routine chest CT (excluding a CT-angiogram), the default timing should be a venous or 60s phase.

TWEAK functions with TNF and IL-17 on keratinocytes and is a potential target for psoriasis therapy

[Figure: see text].

Ultrasonography-Guided Common Musculoskeletal Interventions from Head to Toe: Procedural Tips for General Radiologists

The expanding scope of interventional musculoskeletal procedures has resulted in increased pressure on general radiologists. The confidence of general radiologists in performing ultrasound-guided musculoskeletal procedures varies with their clinical exposure. This didactic review provides a methodologically and clinically oriented approach to enhancing user understanding and confidence in performing ultrasound-guided musculoskeletal procedures. The body of the text is accompanied by figures depicting the procedural approach, injection site, and labeled ultrasonography images. This paper aims to provide a teaching and bedside aid for education on and the execution of musculoskeletal procedures to ensure the provision of quality health care.

TLR9 Sensing of Self-DNA Controls Cell-Mediated Immunity to Listeria Infection via Rapid Conversion of Conventional CD4+ T Cells to Treg

CD4⁺ T lymphocytes are crucial for controlling a range of innate and adaptive immune effectors. For CD8⁺ cytotoxic T lymphocyte (CTL) responses, CD4⁺ T cells can function as helpers (T_H) to amplify magnitude and functionality or as regulatory cells (T_reg) capable of profound inhibition. It is unclear what determines differentiation to these phenotypes and whether pathogens provoke alternate programs. We find that, depending on the size of initial dose, Listeria infection drives CD4⁺ T cells to act as T_H or induces rapid polyclonal conversion to immunosuppressive T_reg. Conversion to T_reg depends on the TLR9 and IL-12 pathways elicited by CD8a⁺ dendritic cell (DC) sensing of danger-associated neutrophil self-DNA. These findings resolve long-standing questions regarding the conditional requirement for T_H amongst pathogens and reveal a remarkable degree of plasticity in the function of CD4⁺ T cells, which can be quickly converted to T_regin vivo by infection-mediated immune modulation.

Dolina et al. show that Listeria infectious dose drives conventional CD4⁺ T cells to act as T_H or mediates conversion to T_reg. Differentiation to T_reg dominates heightened doses and is promoted by CD8α⁺ DC TLR9 engagement of neutrophil self-DNA and IL-12 production, revealing plasticity in the function of CD4⁺ T cells.

The deubiquitinase CYLD controls protective immunity against helminth infection by regulation of Treg cell plasticity

BACKGROUND

Type 2 immunity can be modulated by regulatory T (Treg) cell activity. It has been suggested that the deubiquitinase cylindromatosis (CYLD) plays a role in the development or function of Treg cells, implying that it could be important for normal protective immunity, where type 2 responses are prevalent.

OBJECTIVE

We sought to investigate the role of CYLD in Treg cell function and T_H2 cell immune responses under steady-state conditions and during helminth infection.

METHODS

Foxp3-restricted CYLD conditional knockout (KO) mice were examined in mouse models of allergen-induced airway inflammation and Nippostrongylus brasiliensis infection. We performed multiplex magnetic bead assays, flow cytometry, and quantitative PCR to understand how a lack of CYLD affected cytokine production, homing, and suppression in Treg cells. Target genes regulated by CYLD were identified and validated by microarray analysis, coimmunoprecipitation, short hairpin RNA knockdown, and transfection assays.

RESULTS

Treg cell-specific CYLD KO mice showed severe spontaneous pulmonary inflammation with increased migration of Treg cells into the lung. CYLD-deficient Treg cells furthermore produced high levels of IL-4 and failed to suppress allergen-induced lung inflammation. Supporting this, the conditional KO mice displayed enhanced protection against N brasiliensis infection by contributing to type 2 immunity. Treg cell conversion into IL-4-producing cells was due to augmented mitogen-activated protein kinase and nuclear factor κB signaling. Moreover, Scinderin, a member of the actin-binding gelsolin family, was highly upregulated in CYLD-deficient Treg cells, and controlled IL-4 production through forming complexes with mitogen-activated protein kinase kinase/extracellular receptor kinase. Correspondingly, both excessive IL-4 production in vivo and the protective role of CYLD-deficient Treg cells against N brasiliensis were reversed by Scinderin ablation.

CONCLUSIONS

Our findings indicate that CYLD controls type 2 immune responses by regulating Treg cell conversion into T_H2 cell-like effector cells, which potentiates parasite resistance.

Combination blockade of OX40L and CD30L inhibits allergen-driven memory TH2 cell reactivity and lung inflammation

BACKGROUND

The selective reduction of memory T_H2 cell responses could be key to affording tolerance and protection from the recurrence of damaging allergic pathology.

OBJECTIVE

We asked whether TNF family costimulatory molecules cooperated to promote accumulation and reactivity of effector memory CD4 T cells to inhaled complex allergen, and whether their neutralization could promote airway tolerance to subsequent reexposure to allergen.

METHODS

Mice were sensitized intraperitoneally or intranasally with house dust mite and challenged with intranasal allergen after memory had developed. We assessed whether single or combined blockade of OX40L/CD252 and CD30L/CD153 inhibited memory T cells from driving acute asthmatic lung inflammation and protected mice following exposure to allergen at a later time.

RESULTS

OX40- or CD30-deficient animals showed strong or partial protection against allergic airway inflammation; however, neutralizing either molecule alone during the secondary response to allergen had little effect on the frequency of effector memory CD4 T cells formed and acute lung inflammation. In contrast, a significant reduction in eosinophilic inflammation was observed when OX40L and CD30L were simultaneously neutralized, with dual blockade inhibiting effector memory T_H2 cell expansion in the lungs, whereas formation of peripherally induced regulatory T cells remained intact. Moreover, dual blockade during the secondary response resulted in a tolerogenic state such that mice did not develop a normal tertiary memory T_H2 cell and lung inflammatory response when challenged weeks later with allergen.

CONCLUSION

Memory T-cell responses to complex allergens are controlled by several TNF costimulatory interactions, and their combination targeting might represent a strategy to reduce the severity of inflammatory reactions following reexposure to allergen.

Increased Production of LIGHT by T Cells in Eosinophilic Esophagitis Promotes Differentiation of Esophageal Fibroblasts Toward an Inflammatory Phenotype

BACKGROUND & AIMS

Eosinophilic esophagitis (EoE) is an antigen-mediated eosinophilic disease of the esophagus that involves fibroblast activation and progression to fibrostenosis. Cytokines produced by T-helper type 2 cells and transforming growth factor beta 1 (TGFβ1) contribute to the development of EoE, but other cytokines involved in pathogenesis are unknown. We investigate the effects of tumor necrosis factor superfamily member 14 (TNFSF14, also called LIGHT) on fibroblasts in EoE.

METHODS

We analyzed publicly available esophageal CD3+ T-cell single-cell sequencing data for expression of LIGHT. Esophageal tissues were obtained from pediatric patients with EoE or control individuals and analyzed by immunostaining. Human primary esophageal fibroblasts were isolated from esophageal biopsy samples of healthy donors or patients with active EoE. Fibroblasts were cultured; incubated with TGFβ1 and/or LIGHT; and analyzed by RNA sequencing, flow cytometry, immunoblots, immunofluorescence, or reverse transcription polymerase chain reaction. Eosinophils were purified from peripheral blood of healthy donors, incubated with interleukin 5, cocultured with fibroblasts, and analyzed by immunohistochemistry.

RESULTS

LIGHT was up-regulated in the esophageal tissues from patients with EoE, compared with control individuals, and expressed by several T-cell populations, including T-helper type 2 cells. TNF receptor superfamily member 14 (TNFRSF14, also called HVEM) and lymphotoxin beta receptor are receptors for LIGHT that were expressed by fibroblasts from healthy donors or patients with active EoE. Stimulation of esophageal fibroblasts with LIGHT induced inflammatory gene transcription, whereas stimulation with TGFβ1 induced transcription of genes associated with a myofibroblast phenotype. Stimulation of fibroblasts with TGFβ1 increased expression of HVEM; subsequent stimulation with LIGHT resulted in their differentiation into cells that express markers of myofibroblasts and inflammatory chemokines and cytokines. Eosinophils tethered to esophageal fibroblasts after LIGHT stimulation via intercellular adhesion molecule-1.

CONCLUSIONS

T cells in esophageal tissues from patients with EoE express increased levels of LIGHT compared with control individuals, which induces differentiation of fibroblasts into cells with inflammatory characteristics. TGFβ1 increases fibroblast expression of HVEM, a receptor for LIGHT. LIGHT mediates interactions between esophageal fibroblasts and eosinophils via ICAM1. This pathway might be targeted for the treatment of EoE.

Clearance of apoptotic cells by lung alveolar macrophages prevents development of house dust mite-induced asthmatic lung inflammation

BACKGROUND

Poor clearance of apoptotic cells has been suggested to contribute to severe asthma, but whether uptake of apoptotic cells by lung phagocytes might dampen house dust mite (HDM)-induced lung inflammation has not been shown.

OBJECTIVES

This study investigated whether apoptotic cell engulfment in the murine lung impacts the development of allergen-induced asthmatic airway inflammation and which immune modulating mechanisms were activated.

METHODS

Apoptotic cells were infused into the lungs of mice challenged with HDM allergen and lung inflammation, expression of suppressive molecules, and induction of regulatory T cells were monitored. Additionally, an adenosine receptor agonist was tested to study the mechanism of suppression elicited by apoptotic cells.

RESULTS

Apoptotic cell uptake by lung alveolar macrophages suppressed HDM-driven allergic asthma. This was associated with promoting the regulatory T cell-inducing molecule retinoic acid, inhibiting inflammatory cytokine production, and making macrophages more susceptible to receiving suppressive signals from adenosine. Correspondingly, adenosine receptor agonist treatment also limited HDM-driven allergic airway inflammation through an action on alveolar macrophages.

CONCLUSIONS

These data provide insight into the mechanisms by which lung macrophages dampen allergen-induced airway inflammation. They suggest that targeting lung macrophages to increase their phagocytic capacity, enhance their ability to make retinoic acid, dampen their capacity to make inflammatory cytokines, and increase their responsiveness to adenosine, could be useful to suppress allergic responses.

TL1A Promotes Lung Tissue Fibrosis and Airway Remodeling

Lung fibrosis and tissue remodeling are features of chronic diseases such as severe asthma, idiopathic pulmonary fibrosis, and systemic sclerosis. However, fibrosis-targeted therapies are currently limited. We demonstrate in mouse models of allergen- and bleomycin-driven airway inflammation that neutralization of the TNF family cytokine TL1A through Ab blocking or genetic deletion of its receptor DR3 restricted increases in peribronchial smooth muscle mass and accumulation of lung collagen, primary features of remodeling. TL1A was found as a soluble molecule in the airways and expressed on the surface of alveolar macrophages, dendritic cells, innate lymphoid type 2 cells, and subpopulations of lung structural cells. DR3 was found on CD4 T cells, innate lymphoid type 2 cells, macrophages, fibroblasts, and some epithelial cells. Suggesting in part a direct activity on lung structural cells, administration of recombinant TL1A into the naive mouse airways drove remodeling in the absence of other inflammatory stimuli, innate lymphoid cells, and adaptive immunity. Correspondingly, human lung fibroblasts and bronchial epithelial cells were found to express DR3 and responded to TL1A by proliferating and/or producing fibrotic molecules such as collagen and periostin. Reagents that disrupt the interaction of TL1A with DR3 then have the potential to prevent deregulated tissue cell activity in lung diseases that involve fibrosis and remodeling.

Rhinovirus Infection Promotes Eosinophilic Airway Inflammation after Prior Exposure to House Dust Mite Allergen

Respiratory virus infection normally drives neutrophil-dominated airway inflammation, yet some viral infections result in an eosinophil-dominated response in individuals such as allergic asthmatics. One idea is that viral infection simply exacerbates an ongoing type 2 response to allergen. However, prior exposure to allergen might alter the virus-induced innate response such that type 2-like eosinophilic inflammation can be induced. To test this, mice were sensitized intranasally with house dust mite allergen and then at later times exposed to rhinovirus RV1B via the airways. RV1B infection of naive mice led to the expected neutrophilic lung inflammatory response with no eosinophils or mucus production. In contrast, if mice were exposed to RV1B 1-4 wk after house dust mite inhalation, when the allergen response had subsided, infection led to eosinophilia and mucus production and a much stronger lymphocyte response that were partially or fully steroid resistant. In accordance, RV1B infection resulted in elevated expression of several inflammatory factors in allergen-pre-exposed mice, specifically those associated with type 2 immunity, namely CCL17, CXCL1, CCL2, IL-33, and IL-13. In vitro studies further showed that RV infection led to greater production of chemokines and cytokines in human bronchial epithelial cells that were previously stimulated with allergen, reinforcing the notion of an altered virus response after allergen exposure. In conclusion, we report that prior allergen exposure can modify responsiveness of cells in the lungs such that a qualitatively and quantitatively different inflammatory activity results following virus infection that is biased toward type 2-like airway disease.

Protection against dengue virus requires a sustained balance of antibody and T cell responses

Pre-existing immunity to dengue virus (DENV) can either protect against or exacerbate, a phenomenon known as antibody dependent enhancement (ADE), a secondary DENV infection. DENV, as an escalating health problem worldwide, has increased the urgency to understand the precise parameters shaping the anti-DENV antibody (Ab) and T cell responses, thereby tipping the balance towards protection versus pathogenesis. Herein, we present the current state of knowledge of about the interplay between the Ab and T cell responses that dictate the outcome of DENV infection and discuss how this newfound knowledge is reshaping strategies for developing safe and effective DENV vaccines.

The retrodural space of Okada and its relevance to CT guided intervention

The spinal epidural and posterior ligamentous complex spaces are important anatomic regions which are the target of various radiologic procedures in the cervical, thoracic and lumbar spine for the purpose of analgesia and anaesthesia. Given the frequency with which procedures are performed in and around the epidural space, a sound understanding of the associated anatomy is paramount to ensure the safety and efficacy of procedural intervention.

TNFSF14 (LIGHT) Induces Airway Smooth Muscle Contraction

Asthma is a chronic inflammatory disorder characterized by reversible airway obstruction and airway hyperresponsiveness (AHR). The precise mechanism responsible for AHR is not known but it may involve excess mucus production and alterations in airway smooth muscle cell (SMC) activity. SMC from asthmatic patients are thought to generate more force and contract to a greater extent to allergens or certain inflammatory stimuli, but which inflammatory stimuli in asthmatics drive contraction is still not clear. Previously, we showed that the tumor necrosis factor superfamily member LIGHT (TNFSF14) promotes airway remodeling and AHR in mouse models of chronic asthma, despite having little effect on airway eosinophilia. Exogenous administration of rLIGHT to the mouse airways also induced smooth muscle hyperplasia. We found that LTβR and HVEM, the receptors for LIGHT, are expressed on both human and mouse SMC from the lungs, with LTbR primarily expressed on human cells, suggesting a direct effect of this T cell-derived cytokine. From studies in vitro with primary human SMC, we found that rLIGHT administration induced contraction of SMC in collagen-gels in 3D structures, and migration of SMC in monolayers. rLIGHT induced both actin polymerization and phosphorylation of myosin light chain which leads to actomyosin formation to induce contraction. rLIGHT promoted both canonical and non-canonical NF-kB in airway SMC, and these signals activated the small GTPase Rac1 and P21-Activated Kinase 1 (PAK1) which are involved in actin rearrangement and myosin light chain kinase activity. These results reveal direct evidence that LIGHT can drive SMC contraction and may directly regulate airway hyperresponsiveness relevant to asthma pathogenesis.

Late-rising CD4 T cells show dramatic control of cytomegalovirus persistence

Conventional CD4 T cells typically expand and establish memory pools within the first few weeks of acute viral infection. However, cytomegalovirus (CMV) exhibits an extended persistent replication phase followed by lifelong latency, suggesting the induction, phenotype and/or function of protective memory CD4 T cells may differ. We show that during CMV infection in mice, CD4 T cells recognizing an epitope derived from the viral M09 protein develop long after conventional memory T cells have already formed. These cells are unique compared to their conventional memory counterparts; showing high IFNγ and IL-2 production at times of viral persistence. Ablating these CD4 T cells by mutating the M09 genomic epitope, or inducing them through vaccination, revealed them far superior at resolving persistent replication. RNAseq data reveal that these ‘late-rising’ and conventional CD4 T cells differ dramatically in their transcriptional signatures, and that M09 cells show a uniquely restricted T cell receptor repertoire. We believe these results may help instruct CMV vaccine and cellular immunotherapy approaches in people, and will also provide a blueprint for determining whether similar late-rising CD4 T cells exist in other chronic virus infections.

Shedding LIGHT and TL1A on fibrosis

Anti-inflammatory drugs have so far failed to reduce fibrosis and tissue remodeling in the clinic. Alternatively, 5 TNF inhibitors have been FDA approved to treat different inflammatory diseases and are safe to administer to patients. In human, LIGHT and its receptors have been linked to numerous autoimmune and inflammatory diseases with fibrotic components. We show that blocking LIGHT signaling in isolation is efficient in reducing fibrosis in the skin and lung of mice induced with bleomycin to mimic human SSc and IPF, as well as in 2 severe allergen-driven models of asthma and atopic dermatitis. Neutralizing LIGHT signaling through its receptors by genetic deletion or antibody blocking, dramatically decreased fibrosis in the lungs and skins. Moreover the specific deletion of LIGHT-receptor HVEM on keratinocytes or the therapeutic blocking of LIGHT-HVEM interaction post-disease onset, abrogated skin fibrosis. LIGHT seems to play a central role since it can control the expression of major pro-fibrotic factors such as TSLP, IL-13, TGF-b and Periostin. Also LIGHT alone can induce a fibro-proliferative disorder that mimics human SSc, when administered alone. Lastly we observed an upregulation of LIGHT and its receptors in lung biopsies of patients suffering from asthma, SSc and IPF. More recently, we discovered another TNF family Member called TL1A can also potentiate fibrosis similarly to LIGHT and which signaling can promote tissue remodeling. Using antagonistic fusion proteins to neutralize LIGHT and TL1A signaling, we treated skin fibrosis and observed greater efficacy when LIGHT and TL1A were targeted concomitantly. The relevance of this work to fibrosis therapies associated with asthma, AD, SSc and IPF are tremendous.

Tumor necrosis factor like weak inducer of apoptosis (TWEAK) Promotes Inflammatory Activity in Keratinocytes with IL-17 and TNF to Drive Psoriasis

Psoriasis is an autoimmune skin disease caused by hyper-proliferation of keratinocytes driven by distinct inflammatory cells making cytokines such as IL-17 and TNF. Our previous studies with knockout animals revealed that the TNF-related cytokine TWEAK (TNFSF12) was also a critical contributor to skin inflammation and could be a potential therapeutic target in psoriasis. As Fn14, the receptor for TWEAK, is expressed by keratinocytes, we examined the inflammatory effects of TWEAK alone and with IL-17A and TNF in modulating psoriatic genes in human keratinocytes using RNA-seq. We found that TWEAK upregulated the expression of multiple chemokines and cytokines, such as IL-36G, IL-23A, IL-19, CCL5, CCL20, and other inflammation-associated genes, that have previously been found highly expressed in the skin of patients with psoriasis. TWEAK’s action was partially overlapping with IL-17 and TNF, but interestingly, in combination with IL-17 or TNF, TWEAK had strong synergistic effects in enhancing the expression of a number of these inflammatory genes. We then tested the impact of TWEAK neutralization on already existing skin inflammation in an imiquimod-induced psoriasis model. Mice treated therapeutically with anti-TWEAK showed significantly decreased numbers of immune cell infiltrates in the skin, with fewer γδ T cells, neutrophils and macrophages. These mice also exhibited a marked reduction in epidermal thickening, similar to mice treated with anti-IL-17 alone. Furthermore, co-neutralization of TWEAK and IL-17 demonstrated a greater effect in terms of reducing clinical symptoms. These data suggest that blocking TWEAK could be considered as a potential therapeutic avenue in humans to overcome the pathophysiology of psoriasis.

4-1BBL Regulates the Polarization of Macrophages, and Inhibition of 4-1BBL Signaling Alleviates Imiquimod-Induced Psoriasis

4-1BBL, a member of the TNF superfamily, regulates the sustained production of inflammatory cytokines in macrophages triggered by TLR signaling. In this study, we have investigated the role of 4-1BBL in macrophage metabolism and polarization and in skin inflammation using a model of imiquimod-induced psoriasis in mice. Genetic ablation or blocking of 4-1BBL signaling by Ab or 4-1BB-Fc alleviated the pathology of psoriasis by regulating the expression of inflammatory cytokines associated with macrophage activation and regulated the polarization of macrophages in vitro. We further linked this result with macrophage by finding that 4-1BBL expression during the immediate TLR response was dependent on glycolysis, mitochondrial oxidative phosphorylation, and fatty acid metabolism, whereas the late-phase 4-1BBL-mediated sustained inflammatory response was dependent on glycolysis and fatty acid synthesis. Correlating with this, administration of a fatty acid synthase inhibitor, cerulenin, also alleviated the pathology of psoriasis. We further found that 4-1BBL-mediated psoriasis development is independent of its receptor 4-1BB, as a deficiency of 4-1BB augmented the severity of psoriasis linked to a reduced regulatory T cell population and increased IL-17A expression in γδ T cells. Additionally, coblocking of 4-1BBL signaling and IL-17A activity additively ameliorated psoriasis. Taken together, 4-1BBL signaling regulates macrophage polarization and contributes to imiquimod-induced psoriasis by sustaining inflammation, providing a possible avenue for psoriasis treatment in patients.

The protein tyrosine kinase SYK regulates the alternative p38 activation in liver during acute liver inflammation

Two distinct p38 signaling pathways, classical and alternative, have been identified to regulate inflammatory responses in host defense and disease development. The role of alternative p38 activation in liver inflammation is elusive, while classical p38 signaling in hepatocytes plays a role in regulating the induction of cell death in autoimmune-mediated acute liver injury. In this study, we found that a mutation of alternative p38 in mice augmented the severity of acute liver inflammation. Moreover, TNF-induced hepatocyte death was augmented by a mutation of alternative p38, suggesting that alternative p38 signaling in hepatocytes contributed more significantly to the pathology of acute liver injury. Furthermore, SYK-Vav-1 signaling regulates alternative p38 activation and the downregulation of cell death in hepatocytes. Therefore, it is suggested that alternative p38 signaling in the liver plays a critical role in the induction and subsequent pathological changes of acute liver injury. Collectively, our results imply that p38 signaling in hepatocytes plays a crucial role to prevent excessive liver injury by regulating the induction of cell death and inflammation.

IQGAP1 restrains T-cell cosignaling mediated by OX40

A costimulatory signal from the tumor necrosis factor receptor (TNFR) family molecule OX40 (CD134), which is induced on activated T cells, is important for T-cell immunity. Aberrant OX40 cosignaling has been implicated in autoimmune and inflammatory disorders. However, the molecular mechanism by which the OX40 cosignaling regulates the T-cell response remains obscure. We found that OX40 associated with a scaffold protein, IQ motif-containing GTPase-activating protein 1 (IQGAP1) after ligation by its ligand OX40L. Naïve CD4⁺ T cells from Iqgap1^-/- mice displayed enhanced proliferation and cytokine secretion upon receiving OX40 cosignaling. A C-terminal IQGAP1 region was responsible for its association with OX40, and TNFR-associated factor 2 (TRAF2) bridged these two proteins. The enhanced cytokine response in Iqgap1^-/- T cells was restored by the expression of the C-terminal IQGAP1. Thus, the IQGAP1 binding limits the OX40 cosignaling. Disease severity of experimental autoimmune encephalomyelitis (EAE) was significantly exacerbated in Iqgap1^-/- mice as compared to wild-type mice. Additionally, recipient mice with Iqgap1^-/- donor CD4⁺ T cells exhibited significantly higher EAE scores than those with their wild-type counterparts, and OX40 blockade led to a significant reduction in the EAE severity. Thus, our study defines an important component of the OX40 cosignaling that restricts inflammation driven by antigen-activated T cells.

Antibody-mediated targeting of TNFR2 activates CD8+ T cells in mice and promotes antitumor immunity

Tumor necrosis factor receptor 2 (TNFR2) is the alternate receptor for TNF and can mediate both pro- and anti-inflammatory activities of T cells. Although TNFR2 has been linked to enhanced suppressive activity of regulatory T cells (Tregs) in autoimmune diseases, the viability of TNFR2 as a target for cancer immunotherapy has been underappreciated. Here, we show that new murine monoclonal anti-TNFR2 antibodies yield robust antitumor activity and durable protective memory in multiple mouse cancer cell line models. The antibodies mediate potent Fc-dependent T cell costimulation and do not result in significant depletion of Tregs. Corresponding human agonistic monoclonal anti-TNFR2 antibodies were identified and also had antitumor effects in humanized mouse models. Anti-TNFR2 antibodies could be developed as a novel treatment option for patients with cancer.

An OX40/OX40L interaction directs successful immunity to hepatitis B virus

Depending on age of acquisition, hepatitis B virus (HBV) can induce a cell-mediated immune response that results in either cure or progressive liver injury. In adult-acquired infection, HBV antigens are usually cleared, whereas in infancy-acquired infection, they persist. Individuals infected during infancy therefore represent the majority of patients chronically infected with HBV (CHB). A therapy that can promote viral antigen clearance in most CHB patients has not been developed and would represent a major health care advance and cost mitigator. Using an age-dependent mouse model of HBV clearance and persistence in conjunction with human blood and liver tissue, we studied mechanisms of viral clearance to identify new therapeutic targets. We demonstrate that age-dependent expression of the costimulatory molecule OX40 ligand (OX40L) by hepatic innate immune cells is pivotal in determining HBV immunity, and that treatment with OX40 agonists leads to improved HBV antigen clearance in young mice, as well as increased strength of T cell responses in young mice and adult mice that were exposed to HBV when they were young and developed a CHB serological profile. Similarly, in humans, we show that hepatic OX40L transcript expression is age-dependent and that increased OX40 expression on peripheral CD4⁺ T cells in adults is associated with HBV clearance. These findings provide new mechanistic understanding of the immune pathways and cells necessary for HBV immunity and identify potential therapeutic targets for resolving CHB.

Clearance of Apoptotic cells by Lung Macrophages Prevents Development of House Dust Mite-induced Asthmatic Lung Inflammation

Allergen inhalation can cause epithelial damage and induce cell death while driving asthmatic lung inflammation. It has been suggested that patients with severe asthma may have a defect in clearance of apoptotic cells, of significance as apoptotic cell phagocytosis is thought important to maintain tissue homeostasis. Previously we have reported that lung resident macrophages in a non-inflamed lung generate regulatory T cells (Tregs) and can promote airway tolerance, and hypothesized that this ability was related to uptake of apoptotic cells. We investigated this by infusing apoptotic thymocytes into the lungs to determine their impact on macrophage function and allergic asthma. We found that lung macrophages were the primary cell to engulf apoptotic cells and this was not modified with intranasal exposure to House Dust Mite (HDM) allergen challenge. The uptake of apoptotic cells by alveolar macrophages in vivo or in vitro resulted in increased expression of RALDH1 and RALDH2, enzymes that drive retinoic acid production. When apoptotic cells were transferred into the lung during sensitization with HDM, eosinophilic airway inflammation, and Th2 cytokine production in the BALF and lung, were significantly reduced compared to mice given viable cells. This was accompanied by an increase in the frequency of antigen-specific Treg in the lung draining lymph nodes. These results indicate that apoptotic cell clearance by lung macrophages is important to maintain airway tolerance and prevent induction of allergic asthma.

Inhibition of allergen-specific tissue resident memory Th2 cells through blockade of CD3-mediated signaling ameliorates allergic lung inflammation

Allergic asthma remains a major public health concern, with more than 26 million Americans suffering from the disease. The secretion of cytokines such as IL-4, IL-5, and IL-13 and their ability to persist in the host long after the primary allergen encounter are a reason memory Th2 cells are a major driving force behind allergic asthma morbidity. The selective removal of pre-existing memory Th2 cells could be a key therapeutic venture to enhance tolerance. One such method could involve targeting CD3 through the use of inhibitory anti-CD3 antibodies which successfully induced tolerance in animal models of autoimmune diseases and also show promise in clinical trials. To determine if we could induce airway tolerance, we tested blocking CD3 complex signaling in a HDM model of allergic inflammation. Importantly, pre-sensitized C57BL/6J mice displayed strongly ablated lung inflammation and Th2 responses when treated at the time of memory T cell reactivation with F(ab′)2 anti-CD3 antibody. This treatment was found to inhibit HDM-specific CD4+ T cell proliferation and Th2 cytokine production. Interestingly, while mice treated with anti-CD3 also showed an increased frequency of Treg cells, protection to allergic inflammation was maintained even after Treg depletion. Anti-CD3 treatment was found to specifically inhibit eosinophilic lung inflammation driven by allergen-specific lung tissue resident memory (Trm) Th2 cells as determined by treatment of mice with fingolimod (FTY720), which prevents the recruitment and contribution of circulating memory T cells to the allergic response. These data suggest that blocking CD3 complex signaling could be employed to inhibit Trm recall responses to complex allergens thus promoting airway tolerance.

Accessory Molecule and Costimulation Requirements for CD4 T Cell Response

T cell activation is brought about by recognition of peptide/MHC complexes on an antigen-presenting cell (APC) by the T cell receptor (TCR). However, in general this appears to be insufficient for the full development of T cell responses and therefore additional signals are required, provided by ligation of counter-receptors on the T cell by APC accessory molecules. Although many studies have suggested that B7 molecules (CD80/CD86) binding to CD28 induce this second signal, it is now evident that any one of a number of molecules may provide accessory function and that efficient response is only generated following multiple interactions. It has also become clear that T cells exist in varying states of activation or differentiation, and that requirements for accessory molecules and costimuli are not always equivalent. This review covers much of the recent data regarding accessory molecule regulation of T cell responses. A modified version of the two signal model is presented, suggesting that the major function of accessory molecules during the initial stages of activation is to augment the ability to signal through the TCR, and that the primary role of costimulatory signals is to allow IL-2 secretion and growth. The requirement for multiple accessory molecule interactions is discussed in relation to activation of naive T cells and how such interactions are less critical at the memory and effector stages. Finally, this new information is related to how T cells interact with varying APC and how these interactions may modulate T cell response.

Crystal structure of the m4-1BB/4-1BBL complex reveals an unusual dimeric ligand that undergoes structural changes upon 4-1BB receptor binding

The interaction between the receptor 4-1BB and its ligand 4-1BBL provides co-stimulatory signals for T-cell activation and proliferation. However, differences in the mouse and human molecules might result in differential engagement of this pathway. Here, we report the crystal structure of mouse 4-1BBL and of the mouse 4-1BB/4-1BBL complex, which together provided insights into the molecular mechanism by which m4-1BBL and its cognate receptor recognize each other. Unlike all human or mouse tumor necrosis factor ligands that form noncovalent and mostly trimeric assemblies, the m4-1BBL structure formed a disulfide-linked dimeric assembly. The structure disclosed that certain differences in the amino acid composition along the intramolecular interface, together with two specific residues (Cys-246 and Ser-256) present exclusively in m4-1BBL, are responsible for this unique dimerization. Unexpectedly, upon m4-1BB binding, m4-1BBL undergoes structural changes within each protomer; moreover, the individual m4-1BBL protomers rotate relative to each other, yielding a dimerization interface with more inter-subunit interactions. We also observed that in the m4-1BB/4-1BBL complex, each receptor monomer binds exclusively to a single ligand subunit with contributions of cysteine-rich domain 1 (CRD1), CRD2, and CRD3. Furthermore, structure-guided mutagenesis of the binding interface revealed that novel binding interactions with the GH loop, rather than the DE loop, are energetically critical and define the m4-1BB receptor selectivity for m4-1BBL. A comparison with the human 4-1BB/4-1BBL complex highlighted several differences between the ligand- and receptor-binding interfaces, providing an explanation for the absence of inter-species cross-reactivity between human and mouse 4-1BB and 4-1BBL molecules.

Tumor necrosis factor family member LIGHT acts with IL-1β and TGF-β to promote airway remodeling during rhinovirus infection

BACKGROUND

Rhinovirus (RV) can exacerbate allergen-driven asthma. However, it has been suggested that serial infections with RV may also lead to asthma-like features in childhood without prior allergen exposure.

AIM

We sought to test the effects of RV infection in the absence of allergen challenge on lung tissue remodeling and to understand whether RV induced factors in common with allergen that promote remodeling.

METHODS

We infected C57BL/6 mice multiple times with RV in the absence or presence of allergen to assess airway remodeling. We used knockout mice and blocking reagents to determine the participation of LIGHT (TNFSF14), as well as IL-1β and TGF-β, each previously shown to contribute to lung remodeling driven by allergen.

RESULTS

Recurrent RV infection without allergen challenge induced an increase in peribronchial smooth muscle mass and subepithelial fibrosis. Rhinovirus (RV) induced LIGHT expression in mouse lungs after infection, and alveolar epithelial cells and neutrophils were found to be potential sources of LIGHT. Accordingly, LIGHT-deficient mice, or mice where LIGHT was neutralized, displayed reduced smooth muscle mass and lung fibrosis. Recurrent RV infection also exacerbated the airway remodeling response to house dust mite allergen, and this was significantly reduced in LIGHT-deficient mice. Furthermore, neutralizing IL-1β or TGF-β also limited subepithelial fibrosis and/or smooth muscle thickness induced by RV.

CONCLUSION

Rhinovirus can promote airway remodeling in the absence of allergen through upregulating common factors that also contribute to allergen-associated airway remodeling.

The TWEAK/Fn14 pathway is required for calcineurin inhibitor toxicity of the kidneys

Calcineurin inhibitor toxicity (CNT) is a frequent occurrence in transplanted renal grafts and autochthone kidneys from patients undergoing long-term treatment with calcineurin inhibitors, notably cyclosporin A (CsA) and tacrolimus. Here, we show an indispensable role of the tumor necrosis factor superfamily (TNFS) molecule TNF-related weak inducer of apoptosis (TWEAK) (TNFSF12) in the pathogenesis of acute CNT lesions in mice. A deficiency in TWEAK resulted in limited tubulotoxicity after CsA exposure, which correlated with diminished expression of inflammatory cytokines and reduced intraparenchymal infiltration with immune cells. We further identified tubular epithelial cells of the kidney as major targets of CsA activity and found that Fn14 (tumor necrosis factor receptor superfamily 12A), the receptor for TWEAK, is a highly CsA-inducible gene in these cells. Correlating with this, CsA pretreatment sensitized tubular epithelial cells specifically to the pro-inflammatory activities of recombinant TWEAK in vitro. Moreover, injection of rTWEAK alone into mice induced moderate disease similar to CsA, and rTWEAK combined with CsA resulted in synergistic nephrotoxicity. These findings support the importance of tubular epithelial cells as cellular targets of CsA toxicity and introduce TWEAK as a critical contributor to CNT pathogenesis.

Crystal structures of the human 4-1BB receptor bound to its ligand 4-1BBL reveal covalent receptor dimerization as a potential signaling amplifier

Human (h)4-1BB (TNFRSF9 or CD137) is an inducible tumor necrosis factor receptor (TNFR) superfamily member that interacts with its cognate ligand h4-1BBL to promote T lymphocyte activation and proliferation. h4-1BB is currently being targeted with agonists in cancer immunotherapy. Here, we determined the crystal structures of unbound h4-1BBL and both WT h4-1BB and a dimerization-deficient h4-1BB mutant (C121S) in complex with h4-1BBL at resolutions between 2.7 and 3.2 Å. We observed that the structural arrangement of 4-1BBL, both unbound and in the complex, represents the canonical bell shape as seen in other similar TNF proteins and differs from the previously reported three-bladed propeller structure of 4-1BBL. We also found that the binding site for the receptor is at the crevice formed between two protomers of h4-1BBL, but that h4-1BB interacts predominantly with only one ligand protomer. Moreover, h4-1BBL lacked the conserved tyrosine residue in the DE loop that forms canonical interactions between other TNFR family molecules and their ligands, suggesting h4-1BBL engages h4-1BB through a distinct mechanism. Of note, we discovered that h4-1BB forms a disulfide-linked dimer because of the presence of an additional cysteine residue found in its cysteine-rich domain 4 (CRD4). As a result, h4-1BB dimerization, in addition to trimerization via h4-1BBL binding, could result in cross-linking of individual ligand-receptor complexes to form a 2D network that stimulates strong h4-1BB signaling. This work provides critical insights into the structural and functional properties of both h4-1BB and h4-1BBL and reveals that covalent receptor dimerization amplifies h4-1BB signaling.